/*
* This is the true entry point for untrusted code.
* See nacl_startup.h for the layout at the argument pointer.
*/
void _start(uint32_t *info) {
void (*fini)(void) = nacl_startup_fini(info);
int argc = nacl_startup_argc(info);
char **argv = nacl_startup_argv(info);
char **envp = nacl_startup_envp(info);
Elf32_auxv_t *auxv = nacl_startup_auxv(info);
environ = envp;
/*
* Record the approximate address from which the stack grows
* (usually downwards) so that libpthread can report it. Taking the
* address of any stack-allocated variable will work here.
*/
__nacl_initial_thread_stack_end = &info;
__libnacl_irt_init(auxv);
/*
* If we were started by a dynamic linker, then it passed its finalizer
* function here. For static linking, this is always NULL.
*/
if (fini != NULL)
atexit(fini);
atexit(&__libc_fini_array);
__pthread_initialize();
__libc_init_array();
int (*main_ptr)(int argc, char **argv, char **envp) = &__nacl_main;
if (main_ptr == NULL)
main_ptr = &main;
exit(main_ptr(argc, argv, envp));
/*NOTREACHED*/
__builtin_trap();
}
static void chainload(const char *program, const char *interp_prefix,
int argc, char **argv, int envc, char **envp) {
if (nacl_interface_query(NACL_IRT_RESOURCE_OPEN_v0_1, &resource_open,
sizeof(resource_open)) != sizeof(resource_open))
resource_open.open_resource = NULL;
if (nacl_interface_query(NACL_IRT_CODE_DATA_ALLOC_v0_1, &code_data_alloc,
sizeof(code_data_alloc)) !=
sizeof(code_data_alloc)) {
fprintf(stderr, "Failed to find necessary IRT interface %s!\n",
NACL_IRT_CODE_DATA_ALLOC_v0_1);
exit(1);
}
const size_t pagesize = NACL_MAP_PAGESIZE;
const TYPE_nacl_irt_query irt_query = __nacl_irt_query;
/*
* Populate our own info array on the stack. We do not assume that the
* argv and envp arrays are in their usual layout, since the caller could
* be passing different values.
*/
uint32_t info[NACL_STARTUP_ARGV + argc + 1 + envc + 1 + (kAuxvCount * 2)];
info[NACL_STARTUP_FINI] = 0;
info[NACL_STARTUP_ENVC] = envc;
info[NACL_STARTUP_ARGC] = argc;
memcpy(nacl_startup_argv(info), argv, (argc + 1) * sizeof(argv[0]));
memcpy(nacl_startup_envp(info), envp, (envc + 1) * sizeof(envp[0]));
Elf32_auxv_t *auxv = nacl_startup_auxv(info);
/*
* Populate the auxiliary vector with the values dynamic linkers expect.
*/
auxv[kPhdr].a_type = AT_PHDR;
auxv[kPhent].a_type = AT_PHENT;
auxv[kPhent].a_un.a_val = sizeof(Elf32_Phdr);
auxv[kPhnum].a_type = AT_PHNUM;
auxv[kBase].a_type = AT_BASE;
auxv[kEntry].a_type = AT_ENTRY;
auxv[kSysinfo].a_type = AT_SYSINFO;
auxv[kSysinfo].a_un.a_val = (uint32_t) irt_query;
auxv[kNull].a_type = AT_NULL;
auxv[kNull].a_un.a_val = 0;
/*
* Load the program and point the auxv elements at its phdrs and entry.
*/
const char *interp = NULL;
uint32_t entry = load_elf_file(program,
pagesize,
&auxv[kBase].a_un.a_val,
&auxv[kPhdr].a_un.a_val,
&auxv[kPhnum].a_un.a_val,
&interp);
auxv[kEntry].a_un.a_val = entry;
if (auxv[kPhdr].a_un.a_val == 0)
auxv[kPhdr].a_type = AT_IGNORE;
DEBUG_PRINTF("XXX loaded %s, entry %#x, interp %s\n", program, entry, interp);
if (interp != NULL) {
/*
* There was a PT_INTERP, so we have a dynamic linker to load.
*/
char interp_buf[PATH_MAX];
if (interp_prefix != NULL) {
/*
* Apply the command-line-specified prefix to the embedded file name.
*/
snprintf(interp_buf, sizeof(interp_buf), "%s%s", interp_prefix, interp);
interp = interp_buf;
}
entry = load_elf_file(interp, pagesize, NULL, NULL, NULL, NULL);
DEBUG_PRINTF("XXX loaded PT_INTERP %s, entry %#x\n", interp, entry);
}
for (uint32_t *p = info; p < (uint32_t *) &auxv[kNull + 1]; ++p)
DEBUG_PRINTF("XXX info[%d] = %#x\n", p - info, *p);
/*
* Off to the races!
* The application's entry point should not return. Crash if it does.
*/
DEBUG_PRINTF("XXX user entry point: %#x(%#x)\n", entry, (uintptr_t) info);
(*(void (*)(uint32_t[])) entry)(info);
while (1)
__builtin_trap();
}